But this long run is a misleading guide to current affairs. In
the long run we are all dead. Economists set themselves too easy, too
useless a task if in tempestuous seasons they can only tell us that when the
storm is long past the ocean is flat again.

As I’ve
written before, Keynes’s point here is that economic models are incomplete,
suspect, and not much use if they can’t explain what happens year to year, but
can only tell you where things will supposedly end up after a lot of time has
passed. It’s an appeal for better analysis, not for ignoring the future; and
anyone who tries to make it into some kind of moral indictment of Keynesian
thought has forfeited any right to be taken seriously. ...

I thought the
target of these remarks had forfeited any right to be taken seriously long
ago (except, of course and unfortunately, by Very Serious People). [Krugman goes on to tackle several other topics.]